GE-GE BONDING IN THE HIGH-PRESSURE MODIFICATION OF LITHIUM GERMANIDE - A NEAR-ZINTL PHASE

The Zintl-phase LiGe has recently been shown to undergo a transformation at elevated temperature and pressure to a metastable modification, which differs markedly from the normal-pressure form in the bonding between the Ge atoms. In the normal form the Ge net is exclusively three-connected, but in the high pressure (HP) form there is a mixture of Ge environments. One-third are approximately tetrahedrally four-connected, while the remainder have two short bonds (to the four-connected atoms) and two longer contacts (to other atoms of the same type), arranged in a distorted square plane. Whether or not the longer contacts are ignored, the HP form no longer obeys the electron-counting principles of Zintl or Klemm. In this paper we examine the bonding between the planar four-coordinated atoms and discuss the way the deviation from the Zintl counting rules can be seen to be consistent with the observed structure. © 1990, American Chemical Society. All rights reserved.